Effect of hydrothermal carbonization temperature on fuel properties and combustion behavior of high-ash corn and rice straw hydrochar

Hydrothermal carbonization has been proven to improve the fuel properties of low ash straw biomass. To explore the effect of hydrothermal carbonization on high-ash straw biomass, the fuel properties and combustion behavior of hydrochar prepared by high-ash rice straw and corn straw at different temperature were studied. The results showed that increased reaction temperature could improve the C content, fixed carbon, heating value, and fuel ratios (FC/VM) in high-ash straw hydro chars, which is similar to the change trend of low-ash biomass. The hydrochar prepared at 260 & DEG;C has similar H/C and O/C atomic ratios and FC/VM to lignite. In addition, the highest energetic recovery efficiency is obtained at 200 & DEG;C. While at 180 & DEG;C, the comprehensive combustion characteristic index of the hydrochar is the best, which is 5.04 & BULL; 10-11 [min-2K-3] and 6.42 & BULL; 10-11 [min-2K-3]. In addition, the C content in the hydrochars at 180 & DEG;C was lower than the raw material, and the ash content increases with the reaction temperature, which is quite different from the low-ash biomass. In conclusion, the hydrothermal carbonization could improve the fuel quality of high-ash straw, while its ash content remains at a high level.